#include <bits/stdc++.h>
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
const int nmax=10010;
int i,j,n,wmax,w[1001],c[1001],e[1001][5001];
int main()
{
    fin>>n;
    fin>>wmax;
    for(i=1;i<=n;i++)
    {
        fin>>w[i];
        fin>>c[i];
    }

    for(i=0;i<=n;i++)
        for(j=0;j<=wmax;j++)
            e[i][j]=nmax;

    for(i=1;i<=n;i++)
        for(j=1;j<=wmax;j++)
        {
            e[i][j]=e[i-1][j];
            if(j-w[i]>0)
                e[i][j]=min(e[i][j],e[i-1][j-w[i]]+c[i]);
            else
                e[i][j]=min(e[i][j],c[i]);
        }
    if(e[n][wmax]==nmax)fout<<-1;
    else fout<<e[n][wmax];
    return 0;
}